Utilizing feather hormone measurements to study avian welfare

Abstract

Feathers offer a non-invasive method for assessing the welfare of birds in human care. However, because few studies have utilized feather hormone measurements, little data exist for most taxa. Here, we measured concentrations of two hormones associated with welfare, corticosterone (CORT) and dehydroepiandrosterone-suphate (DHEA-S), and calculated CORT/DHEA-S ratios in feathers (n=979) from 46 individuals comprising 10 species of birds at the World Bird Sanctuary. Hormone concentrations based on feather mass and length were measured for primary and secondary wing feathers, and tail feathers. Concentrations were compared among feather types, and the variability in concentrations within feather types from individual birds was assessed. We also determined whether factors often associated with welfare, specifically sex, age, housing conditions, and participation in ambassador programs, were correlated with differences in hormone concentrations. We found that hormone concentrations differed significantly among feather types, with tail feathers having higher concentrations of CORT and DHEA-S compared to wing feathers. Concentrations of both hormones were less variable in tail feathers compared to wing feathers. Significant differences in hormone concentrations were also observed across taxa and in relation to sex and age. Ambassador birds had higher CORT/DHEA-S ratios than non-ambassador individuals, and birds participating in programs year-round had higher CORT/DHEA-S ratios than birds that participated in programs for 6 months of the year. Birds housed behind-the-scenes had lower concentrations of feather CORT and CORT/DHEA-S ratios than birds housed in view of guests year-round. These results provide comparative data and methodological recommendations for future studies of feather hormones.